Subject testing arises in a wide variety of contexts and ranges from posing a battery of test questions to eliciting a subject's response to different types of stimuli. A prime example of the latter type of testing is the technique used to fit a hearing-impaired subject, or patient, with a cochlear implant system. Once a such a system is implanted, as with many other types of digital hearing-enhancement systems, a suitable speech coding and mapping strategy must be selected to enhance the performance of the system for day-to-day operation. The mapping strategy pertains to an adjustment of parameters corresponding to one or more independent channels of a multi-channel cochlear implant or other hearing-enhancement system. Selection of each strategy typically occurs over an introductory period of approximately six or seven weeks, during which the hearing-enhancement system is tuned for the particular patient. During this tuning period, users of such systems are asked to provide feedback on how they feel the device is performing.
More particularly, to create a mapping for a speech processor, an audiologist first determines the electrical dynamic range for each electrode or sensor used. The programming system delivers an electrical current through the hearing-enhancement system to each electrode in order to obtain the electrical threshold (T-level) and comfort or “max” level (C-level) measures defined by a system's manufacturer. T-level, or minimum stimulation level, is the minimum electrical current capable of producing an auditory sensation in the user 100 percent of the time. The C-level is the loudest level of signal to which a user can listen comfortably for a long period of time.
A speech processor then is programmed or “mapped” using one of several encoding strategies so that the electrical current delivered to the implant will be within this measured dynamic range; that is between the T- and C-levels. After T- and C-levels are established and the mapping is created, the microphone is activated so that the patient is able to hear speech and other sounds. From that point onwards, the tuning process continues as a traditional hearing test. Hearing-enhancement device users are asked to listen to tones of varying frequencies and amplitudes. The gain of each channel can be further altered within the established threshold ranges such that the patient is able to hear various tones of varying amplitudes and frequencies reasonably well.
Not surprisingly, fitting and tuning a hearing-enhancement system of any type so as to meet the needs of a particular patient is typically quite costly and very time consuming, both from the perspective of the hearing-impaired patient and the audiologist. The functions of such a system are regulated by a large number of parameters, values for each of which typically must be determined so as to tune the system to provide optimal performance for the particular patient. In order to do so, the patient typically must be thoroughly tested with respect to each of set of parameter values. The number of tests generally increases exponentially as the number of system parameters increases.
More generally, the problems inherent in testing a hearing-impaired patient so as to optimally set the system parameters values for a hearing-enhancement system arise with various other types of qualitative or quantitative tests in which a subject has to respond to posed test questions or physical stimuli. Many testing techniques, such as those utilized for tuning a hearing-enhancement system as described above, require a substantial investment of time and effort. Accordingly, there is a need for a technique that in such contexts is able to reduce testing time without compromising the quality of the testing performed.